Galactic cosmic rays, propagation, gamma-rays and neutrinos

Galactic cosmic rays, propagation, gamma-rays and neutrinos Andrii Neronov APC Paris & EPFL Lausanne All particles Galactic cosmic rays, propagation, gamma-rays and neutrinos Galactic Galactic+ extragalactic extragalactic ? All particles Galactic cosmic rays, propagation, gamma-rays and neutrinos •What cosmic rays originate from Galactic sources, at what energy is “galactic to extragalactic” transition? Galactic All particles knee ? •What cosmic rays originate from Galactic sources, at what energy is “galactic to extragalactic” transition? •What is the nature of its PeV “knee” feature? Galactic cosmic rays, propagation, gamma-rays and neutrinos Galactic knee ? LHAASO collaboration, 2505.14447 protons •What cosmic rays originate from Galactic sources, at what energy is “galactic to extragalactic” transition? •What is the nature of its PeV “knee” feature? Galactic cosmic rays, propagation, gamma-rays and neutrinos Galactic knee ? protons ? 10 TeV bump Sub-TeV “ankle” ? DAMPE Collaboration 1909.12860 •What cosmic rays originate from Galactic sources, at what energy is “galactic to extragalactic” transition? •What is the nature of its PeV “knee” feature? •What is the nature of other features: •10 TeV ”bump” •sub-TeV “ankle” •…. Galactic cosmic rays, propagation, gamma-rays and neutrinos •What cosmic rays originate from Galactic sources, at what energy is “galactic to extragalactic” transition? •What is the nature of its PeV “knee” feature? •What is the nature of other features: •10 TeV ”bump” •sub-TeV “ankle” •…. •Is the cosmic ray spectrum “universal” across the Galaxy? Sun Milky Way Galactic cosmic rays, propagation, gamma-rays and neutrinos Sun Milky Way advection diffusion streaming escape Features in the Galactic cosmic ray spectrum may arise because of •changes of regime of propagation of cosmic rays in the interstellar medium Galactic cosmic rays, propagation, gamma-rays and neutrinos Sun Milky Way population A population B population C Features in the Galactic cosmic ray spectrum may arise because of •changes of regime of propagation of cosmic rays in the interstellar medium •or existence of different source populations Galactic cosmic rays, propagation, gamma-rays and neutrinos •What cosmic rays originate from Galactic sources, at what energy is “galactic to extragalactic” transition? •What is the nature of its PeV “knee” feature? •What is the nature of other features: •10 TeV ”bump” •sub-TeV “ankle” •…. •Is the cosmic ray spectrum “universal” across the Galaxy? Sun Milky Way Galactic cosmic rays, propagation, gamma-rays and neutrinos Can 𝜸-ray and neutrino data provide answers to those questions? Sun Milky Way Galactic cosmic rays, propagation, gamma-rays and neutrinos expected 𝛾-ray spectrum shape Prevotat et al. 2507.10823 Slopes of the spectra of 𝛾-rays and neutrinos from cosmic ray interactions closely follow the slope of the parent cosmic ray spectrum. Features in the parent cosmic ray spectrum (e.g. the knee) induce features in the spectra of 𝛾-rays and neutrinos, at an order-of-magnitude lower energy. knee Γ≃2.64 Milky Way magnetic field model Cosmic ray nuclei and electrons interact in the interstellar medium and produce 𝛾-rays and neutrinos. Diffuse 𝛾-ray emission flux is dominated by the pion decay component (0.85 of the total diffuse at GeV energy). 𝑵+𝑁→𝑁+𝜋5,±;' 𝜋5→𝜸+𝜸 𝒆+𝛾→𝑒+𝜸;' 𝒆+𝑁→𝑒+𝑁+𝜸 Pion decay 𝜈 Inverse Compton Bremsstrahlung cosmic ray nucleon cosmic ray electron 𝜋±→𝑒,𝜇,𝝂𝒆,𝝂_𝝁 Pion decay 𝛾 Pion decay Inverse Compton Bremsstrahlung Fermi/LAT Collab. 1202.4039, 1602.07246 Milky Way Sun Galactic cosmic rays, propagation, gamma-rays and neutrinos Fermi/LAT E>1 GeV Milky Way magnetic field model Cosmic ray nuclei and electrons interact in the interstellar medium and produce 𝛾-rays and neutrinos. Diffuse 𝛾-ray emission flux is dominated by the pion decay component (0.85 of the total diffuse at GeV energy). 𝑵+𝑁→𝑁+𝜋5,±;' 𝜋5→𝜸+𝜸 𝒆+𝛾→𝑒+𝜸;' 𝒆+𝑁→𝑒+𝑁+𝜸 Pion decay 𝜈 Inverse Compton Bremsstrahlung cosmic ray nucleon cosmic ray electron 𝜋±→𝑒,𝜇,𝝂𝒆,𝝂_𝝁 Pion decay 𝛾 Milky Way Sun Galactic cosmic rays, propagation, gamma-rays and neutrinos pion decay IceCube Collab. 2307.04427 Milky Way Sun Galactic cosmic rays, propagation, gamma-rays and neutrinos IceCube Collab. 2307.04427 𝜈,'all-sky template “𝜋!” 𝛾,'all-sky Fermi/LAT 𝜈,'all-sky templates “KRA𝛾” 𝛾-ray – neutrino consistency check Milky Way magnetic field model Milky Way Sun Galactic cosmic rays, propagation, gamma-rays and neutrinos IceCube Collab. 2307.04427 𝜈,'all-sky template “𝜋!” 𝛾,'all-sky Fermi/LAT 𝜈,'all-sky templates “KRA𝛾” 𝛾-ray – neutrino consistency check Γ=2.5 ×8 Galactic neutrino flux estimate at 1 TeV is much the all-sky 𝛾-ray flux measurement in “KRA𝛾 template” neutrino signal models. Milky Way magnetic field model Milky Way Sun Galactic cosmic rays, propagation, gamma-rays and neutrinos IceCube Collab. 2307.04427 𝜈,'all-sky template “𝜋!” 𝛾,'all-sky Fermi/LAT 𝜈,'all-sky templates “KRA𝛾” 𝛾-ray – neutrino consistency check Γ=2.64 Galactic neutrino flux estimate at 1 TeV is consistent with total allsky 𝛾-ray flux measurement in “𝜋5 template” neutrino signal model. better match with 𝛾-ray data at 1 TeV Galactic neutrino flux estimate at 1 TeV is much the all-sky 𝛾-ray flux measurement in “KRA𝛾 template” neutrino signal models. Milky Way magnetic field model Cosmic ray nuclei and electrons interact in the interstellar medium and produce 𝛾-rays and neutrinos. Diffuse 𝛾-ray emission flux is dominated by the pion decay component (0.85 of the total diffuse at GeV energy). 𝑵+𝑁→𝑁+𝜋5,±;' 𝜋5→𝜸+𝜸 𝒆+𝛾→𝑒+𝜸;' 𝒆+𝑁→𝑒+𝑁+𝜸 Pion decay 𝜈 Inverse Compton Bremsstrahlung cosmic ray nucleon cosmic ray electron 𝜋±→𝑒,𝜇,𝝂𝒆,𝝂_𝝁 Pion decay 𝛾 Milky Way Sun Galactic cosmic rays, propagation, gamma-rays and neutrinos IceCube Collab. 2307.04427 𝜈,'all-sky template “𝜋!” 𝛾,'all-sky Fermi/LAT 𝜈,'all-sky templates “KRA𝛾” 𝛾-ray – neutrino consistency check Γ=2.64 Galactic neutrino flux estimate at 1 TeV is consistent with total allsky 𝛾-ray flux measurement in “𝜋5 template” neutrino signal model. Is cosmic ray spectrum the same everywhere across the Galactic disk? better match with 𝛾-ray data at 1 TeV Milky Way magnetic field model Cosmic ray nuclei and electrons interact in the interstellar medium and produce 𝛾-rays and neutrinos. Diffuse 𝛾-ray emission flux is dominated by the pion decay component (0.85 of the total diffuse at GeV energy). 𝑵+𝑁→𝑁+𝜋5,±;' 𝜋5→𝜸+𝜸 𝒆+𝛾→𝑒+𝜸;' 𝒆+𝑁→𝑒+𝑁+𝜸 Pion decay 𝜈 Inverse Compton Bremsstrahlung cosmic ray nucleon cosmic ray electron 𝜋±→𝑒,𝜇,𝝂𝒆,𝝂_𝝁 Pion decay 𝛾 Galactic cosmic rays, propagation, gamma-rays and neutrinos IceCube Collab. 2307.04427 𝜈,'all-sky template “𝜋!” 𝛾,'all-sky Fermi/LAT 𝜈,'all-sky templates “KRA𝛾” 𝛾-ray – neutrino consistency check Γ=2.64 Galactic neutrino flux estimate at 1 TeV is consistent with total allsky 𝛾-ray flux measurement in “𝜋5 template” neutrino signal model. better match with 𝛾-ray data at 1 TeV Inner galaxy Inner Galaxy Outer Galaxy Milky Way magnetic field model Inner Galaxy Outer Galaxy Galactic cosmic rays, propagation, gamma-rays and neutrinos Spectrum of 𝛾-ray emission from the Inner Galactic disk is harder (slope Γ≃ 2.45) than expected under the hypothesis of ”universal” cosmic ray spectrum across the Galaxy. The brightest part of the Inner Galactic disk in gamma-rays is the “Galactic Ridge”. It outlines the region within 4 kpc distance whith the highest star formation rate. HESS Collab., 1411.7568 AN, Semikoz, 1907.06061 AN, Malyshev, 1505.0760 spectral slope Flux at 10 GeV Γ = 2.64 Galactic cosmic rays, propagation, gamma-rays and neutrinos IceCube “segments” Neste et al. (for IceCube Collab.), 2507.08097 IceCube has also reported the neutrino flux from different segments of the Galactic plane,…. however, signal statistics is limited….. Galactic Ridge segment (1) Galactic cosmic rays, propagation, gamma-rays and neutrinos Inner Galaxy (15∘<𝑙<125∘) Fermi-LAT, diffuse LHAASO, diffuse LHAASO, total Inner Galaxy Prevotat et al. 2407.11911, 2507.10823 Outer Galaxy (125∘< 𝑙 < 235∘) Outer Galaxy Fermi-LAT, total Galactic cosmic rays, propagation, gamma-rays and neutrinos Inner Galaxy (15∘<𝑙<125∘) Inner Galaxy Prevotat et al. 2407.11911, 2507.10823 Outer Galaxy (125∘< 𝑙 < 235∘) Outer Galaxy Inverse Compton, unresolved sources (?) Galactic cosmic rays, propagation, gamma-rays and neutrinos LHAASO measurements of diffuse emission in 0.1-1 PeV energy range are in tension with predictions for diffuse emission flux based on assumption of identical cosmic ray spectrum across the Galactic disk. Inner Galaxy (15∘<𝑙<125∘) Inner Galaxy Prevotat et al. 2407.11911, 2507.10823 Outer Galaxy (125∘< 𝑙 < 235∘) Outer Galaxy model based on local CR spectrum excess Is the “knee” of the cosmic ray spectrum variable across the Galactic disk? Galactic cosmic rays, propagation, gamma-rays and neutrinos Inner Galaxy (15∘<𝑙<125∘) Inner Galaxy Prevotat et al. 2407.11911, 2507.10823 Outer Galaxy (125∘< 𝑙 < 235∘) Outer Galaxy model based on local CR spectrum excess Is the “knee” of the cosmic ray spectrum variable across the Galactic disk? Intermittent source population? Local source? Intermittent source population? Local source? Summary Good prospects for answering the questions about cosmic ray spectrum: •What is the nature of its PeV “knee” feature? •What is the nature of other features, like 10 TeV bump? •Is the cosmic ray spectrum “universal” across the Galaxy? with a combination of 𝛾-ray and neutrino data. Already available data hint at •variable slope of cosmic ray spectrum across the Galactic disk (?) •variable position of the knee of cosmic ray spectrum (?) all-sky Galactic Ridge